CN1505738A - Hydraulic piston position sensor - Google Patents

Hydraulic piston position sensor Download PDF

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Publication number
CN1505738A
CN1505738A CNA02809042XA CN02809042A CN1505738A CN 1505738 A CN1505738 A CN 1505738A CN A02809042X A CNA02809042X A CN A02809042XA CN 02809042 A CN02809042 A CN 02809042A CN 1505738 A CN1505738 A CN 1505738A
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CN
China
Prior art keywords
piston
cylinder
bar
slider
fixed
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Granted
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CNA02809042XA
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Chinese (zh)
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CN1250883C (en
Inventor
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格雷戈里·C·布朗
E
布赖恩·E·里克特
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Rosemount Inc
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Rosemount Inc
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/28—Means for indicating the position, e.g. end of stroke
    • F15B15/2815—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT
    • F15B15/2869—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT using electromagnetic radiation, e.g. radar or microwaves

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Toxicology (AREA)
  • Electromagnetism (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Health & Medical Sciences (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Actuator (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Length-Measuring Devices Using Wave Or Particle Radiation (AREA)

Abstract

A piston (14) position in a cylinder (12) of a hydraulic assembly (10) is measured using microwave pulses. The microwave pulses are launched along a conductor (22) coupled to the piston (14) or cylinder (12). A sliding member (34) is slidably coupled to the conductor (22) and moves with the piston (14) or cylinder (12) .Position is determined as a function of a reflection from the end (32) of the conductor (22) and the sliding member (34).

Description

Hydraulic piston position sensor
Technical field
The present invention relates to hydraulic piston.The invention particularly relates to the piston sensor that is used to detect the relative position between piston and the hydro cylinder.
Background technique
Various types of displacement transducers are used to measure the relative position of piston in hydro cylinder.Yet the device of telemeasurement absolute position is complicated and expensive highly reliably under rugged environment at present.An example of presently used technology is magnetostriction (magnitostrictive) device, it uses the loss time (time of flight) along the mechanical signal that is encapsulated in a pair of fine rule in the sealed metal tube, and described mechanical signal is to respond to change from the magnetostriction of the mechanical property of bar to reflect.Another technology is used absolute rotating coder, and it is a kind of device that detects rotation.Straight line motion and rotatablely move between conversion by finishing with gear, the perhaps cable that launches by reel (cable) or bring and finish from elastic load.Absolute encoder is easy to be subjected to the restriction of limited scope and/or resolution.The rugged environment that comprise high levels of vibrations may be got rid of the consideration to absolute etching glass calibrated scale, this be since their strictness to alignment request, to the receptance of brittle fracture and to the low tolerance of mist and dirt.This technology also needs rezeroed frequency.
Such as having had some difficulties by the such inferred position method of measurement of translational movement that the volume flowrate that flows into cylinder is assigned to calculate cylinder to the time quadrature.At first, these devices be increment (incremental) and require frequent manually making zero.The second, they are for responsive such as environmetal impacts such as temperature and density.They need measure these variablees so that accurate displacement measurement to be provided.At last, the integration flow is measured displacement and might be reduced measuring accuracy.This technology also is subjected to the restriction of the dynamic detection range of flow measurement range.This more than scope or following flow have very big error.
In U.S. Pat 5,977,778, US6,142,059 and WO 98/23867 in a kind of technology of utilizing the EMP (Electromagnetic Pulse) measurement piston position has been described.But this technology is easy to the environmental radiation radioactive rays and is difficult to calibration.
Summary of the invention
A kind ofly be used for measuring the device of hydraulic piston, comprise the bar that extends along the piston motion direction, and described bar is fixedly connected in piston or the cylinder one of them at the relative position of cylinder.Described bar is constructed to deliver microwave pulse.One slider is connected on the described bar slidably and is fixedly connected in piston or the cylinder another.Described sliding contact part is constructed to cause the partial reflection of microwave pulse.The bar end also is provided with reverberation.Can calculate piston position as function from the reflected microwave pulse of sliding contact part and boom end.
Description of drawings
Figure 1A is the sectional side view that comprises the hydraulic pressure installation of piston measuring circuit.
Figure 1B is the top sectional drawing of cutting open along the tag line 1B-1B shown in Figure 1A.
Fig. 2 A is the sectional side view that comprises the hydraulic pressure installation of piston measuring circuit.
Fig. 2 B is the top sectional drawing of cutting open along the tag line 2B-2B shown in Fig. 2 A.
Fig. 3 is the sectional side view of hydraulic system, and its king-rod is positioned at the outside of cylinder.
Fig. 4 is the sectional side view of hydraulic system, and wherein piston is used to position measurement.
Fig. 5 is the sectional side view of link.
Fig. 6 shows the hydraulic system that comprises the position measurement circuit Block Diagram.
Embodiment
Figure 1A and Figure 1B are the sectional side view and the top sectional drawings of described according to one embodiment of present invention hydraulic piston/cylinder unit 10.Device 10 comprises cylinder 12, and cylinder 12 delivers piston 14 therein slidably, and piston 14 is connected on the bar 16.Piston 14 moves in cylinder 12 in response to hydraulic fluid 18, and hydraulic fluid 18 adds the inside of cylinder 12 by opening 19 or extracts out from the inside of cylinder 12.Sealing 20 extends to prevent the hydraulic fluid seepage around piston 14.Bar 22 extends and is connected to piston measuring circuit 24 along the length of cylinder 12.Position measurement circuit 24 is connected to bar 22 by break-through link 38.Opening 26 is set so that hydraulic fluid flows in the cavity 30 of piston 14 on piston 14.But end 32 supported parts 34 of bar 22 are supported.
In operation, when hydraulic fluid 18 was injected into cylinder 12 or discharges from cylinder 12, piston 14 slided in cylinder 12.The piston 14 also bar in the cavity 30 that is contained in piston 14 22 slides.When piston 14 was mobile in cylinder 12, contact guidance spare 40 was across on bar 22.Although illustrated bar 22 is fixed on the cylinder 12.They also can be fixed on the piston 14 and with respect to cylinder 12 and move.
Position measurement circuit 24 produces position output according to the reflected wave from the microwave signal that is connected to bar 22.Two positions of microwave signal on bar 22 are reflected: promptly at contact guidance spare or lining 40 places and boom end 32 places.Position measurement circuit is measured the relative position of piston 14 in cylinder 12 in response to the time lag ratio between two reflected signals.
In the present embodiment, the present invention utilizes little Time Domain Reflectometry radar MTDR (Micro TimeDomain Reflectometry Radar).The MTDR technology is a kind of loss time measurement technology.Accurately pulse that limits or pulsed microwave radar signal are coupled in the transmission line of the shape that makes two parallel conductors.The geometrical shape of preferred this pair of parallel conductor is because the electromagnetic interference (EMI) of its restriction radiation.Be responsible for to produce radar signal, be coupled to radar signal in the transmission line and the device of detected reflectance signal is known as transducer at this.
Basic MTDR measurement is achieved in that along transmission line length, very thin of all bars 22 as shown in Figure 1 and so on and sends radar pulse, and highly precisely measurement signal is delivered to pip and returns the required time.This pip can begin from the end 32 of transmission line or from second mechanical body such as supporter 34 along length of transmission line contact (or contiguous) transmission line, for example the sliding contact part 40.If this mechanical body (slider 40) is moved along the length of transmission line, its position can be measured by the time of passing through of its blip.Particularly, produce the reference radar pulse of the end 32 be sent to the transmission line that forms by bar 22 and to its timing.Make comparisons with the time of passing through of the pulse of being reflected then by the sliding mechanical body.An advantage of this technology is to measure to be independent of transmission line medium on every side.
Another advantage of this surveying is, measuring frequency is enough fast, so that in time demarcation of location is measured, thereby can obtain the speed and the acceleration of piston when needing.In addition, by the geometrical shape of transmission line suitably is set, also can the measured angular displacement.
One embodiment of the present of invention comprise uses dual component transmission line (dual elementtransmission line).This provides two kinds of functions.At first, thus it comprises the regulation that government is satisfied in radiation.The second, in various embodiments, second transmission line can be a cylinder casing itself.This is because test rod can prevent the influence that its dielectric false (spurious) that is subjected to the cylinder outside changes, and for example applies mud or other exterior materials.In a preferred embodiment, the invention provides a kind of temporary protection scheme so that when surge is applied on the cylinder casing, prevent electronic failure.
Another aspect of the present invention comprises along the control of the connection of the circuit between frequency generating circuit and the sense transmission line to transition of mechanical impedance.Preferably seamlessly transit.Preferably, by realizing seamlessly transitting in the spacing that changes gradually more than the length of 〉=1/4 pulse wavelength between the earth and the conductor.The impedance mismatching of non-gradual change shows as the blip of loop (ring)/return measurement circuit.The narrow limitation of the position of time measurement is, several inches of beginning normally most are difficult to measure, this owing to blip must have very high " Q " so that from original pulse, distinguished.Design relatively poor impedance mismatching and produce low " Q " reflected signal, cause being difficult to measure near the displacement of dead-center position.
Fig. 2 A and Fig. 2 B are according to the sectional side view of another embodiment's hydraulic system 58 and top sectional drawing.In Fig. 2 A and Fig. 2 B, the element that is similar to Figure 1A and 1B is marked by identical label.In Fig. 2 A and Fig. 2 B, two independent electric-conducting stems of single bar 60 deliveries.This structure has reduced the number of openings that must be provided with in piston 14.Opening 61 makes fluid flow through guide body 14.
Fig. 2 C is the part broken-open perspective view according to another embodiment's hydraulic system 70.In Fig. 2 C, guide 34 and 40 slides in piston rod 16, and has the opening 16 that forms therein.Break-through link 38 extends from the pedestal 72 of cylinder 12.
Fig. 3 is the sectional drawing according to another embodiment's hydraulic system 100.In the embodiments of figure 3, lever arrangement 102 is arranged on the outside of cylinder 12.Bar 104 is affixed on the piston 14 at connection 106 places, and slides in contact guidance spare 108.The advantage of this structure is that piston 14 and cylinder 12 do not need to transform.Housing 109 can be a kind of metal so that shielding to be provided, and whole device 100 can be connected to electrical ground so that prevent from the false radiation of the microwave signal that free position measurement circuit 24 produces.
Fig. 4 shows the hydraulic system 120 according to another embodiment.Produce reflection in the end 123 of piston 14 and the end 125 of cylinder 12.Similar Figure 1A is marked by identical label with element among the 1B.In Fig. 4, be provided with second antenna element (antenna member) 122 of conduction, it is around cylinder 122 and be connected to electric institute grounding end.In this embodiment, cylinder or piston are coated with non-conducting material.Second antenna element 122 can be sleeve pipe or metallic rod according to external environment condition.(preferably, the corrosion-resistant material with suitable dielectrics or material can be a conductor).Second antenna element 122 is connected on the piston 14 and with piston 14 and moves.Piston 14 is connected to piston measuring circuit 24.In this embodiment, signal source can be directly coupled to the pedestal metal of cylinder and from the reflected signal of the end of the cylinder of being surveyed.Cylinder and piston also can drive with radar signal with opposite structure.The second outside conductive jacket can surround cylinder and/or piston in case locking system to environmental radiation.
Fig. 5 is connected to for example sectional drawing of the link 38 of concentric cable circuit 140.Cable run 140 is connected on the through hole (feedthrough) 142, and through hole 142 is connected on the microstrip circuit 144 successively.Transmission pole 146 extends and enters the inside of cylinder 12 by mounting 148.Whole device is surrounded by through hole 150.
Fig. 6 shows the hydraulic system 180 of the Block Diagram that comprises position measurement circuit 24.Position measurement circuit 24 is connected on the link 38 and comprises microwave transceiver 182 and counting circuit 184.Microwave transceiver circuit 182 comprises pulse oscillator 186 and the pulse receiver 188 by the known technology operation.Such technology for example is disclosed in the U.S. Pat 5,361,070 of the promulgation in 1 day November in 1994 of all being presented to McEwan, the U.S. Pat 5 of promulgation on November 7 nineteen ninety-five, 465, in the U.S. Pat 5,609,059 of promulgation on March 11st, 094 and 1997.As mentioned above, counting circuit 184 is measured the position of piston (not shown in Fig. 6) with respect to cylinder 12 according to two time lag ratios that return between the pulse.One of them returns pulse is end from bar, and another is from the sliding contact part that slides along bar.According to this ratio, counting circuit 184 provides position output.This can realize in microprocessor or other logical circuit.In addition, can constitute analog circut so that the output relevant with the position to be provided.
The present invention utilizes two ratios between the reflected signal to measure piston position.A reflected signal can transmit from point of contact along " gauge rod (dipstick) ", and another signal can be from the end reflections of bar.Ratio between these two signal propagation times can be used to measure piston position.This technology does not need the dielectric change (dielectric variation) in the separate compensation hydraulic oil.
All aspects of of the present invention comprise piston or cylinder translation measurement device, and it utilizes MTDR loss time technology.Dual component MTDR can be provided transmission line, and it has the needed translation length of the measurement of being fit to.The dual component transmission line also is desirable, and this is because it has reduced stray radiation.Preferably, provide link so that inverting element is connected to the dual component transmission line.Certain contact should move along transmission line, and provides impedance mismatching to cause the reflection in transmission line.Transducer and/or signal modulation electronics can be sealed in order to avoid be subjected to the influence of severe environmental conditions.Can provide simulation, numeral or light link so that with measured position and external device communication.
The dual component transmission line can be made of two independent conductive paths.For example, this can form with two bars that have or do not have insulator.Described bar can extend substantially abreast along the length of transmission line.Described one or more bar can be fixed on the cylinder, and the point of contact that is connected to piston can move along the length of bar.Described point of contact also can provide support for bar.Described support can reduce or prevent the excessive deviation under height vibration or other stress condition.Link can be provided so that be connected on the bar by cylinder wall.
Various structures can be used among the present invention.For example, conversion element, signal generator and signal processing electronic device can be installed in be arranged on the cylinder or with the isolated environmental protection shell of cylinder.The duplicate transmissions line can be formed by two conductors that are embedded in the non-conducting material that is roughly rigidity.Described conductor can extend along the length of transmission line with being essentially parallel to each other.Described conductor can be placed on the form that single pole is made in the insulating material neutralization.Preferably, described material is fit to long term exposure in the nytron substance environment, for example is present in those materials in the hydro cylinder.
Can provide loss or the degeneration of diagnosis, perhaps the transmission line of fracture or degeneration with the identification point of contact.Point of contact (slider) can be made the material that preferred permittivity is different in essence by the material that has a differing dielectric constant with the material that forms transmission line.Such examples of material can comprise: aluminium oxide contact and/or glass-filled PEEK.Can provide any point of contact that slides along transmission line, for example roller (roller) or bluff body (blunt body).Can utilize any known technology to push point of contact to transmission line, described technology comprises spring, magnetic device or fluid means.Yet, do not need physics contact (physical contact).
Although described the lining bar of two conductors, other embodiment also is feasible, and wherein, cylinder itself can be counted as a conductor, and a solid rod can be used in the cylinder.In such embodiments, importantly cylinder casing itself is maintained at signal ground (signal-ground) and locates.In general, for the embodiment of two-conductor, preferably one of them conductor is fixed on signal ground.
In the present invention, provide absolute measurement, do not needed system to make zero.Described system is potential can be with less than positive and negative 1 millimeter precision measure position of piston.The maximum of described system is measured length (span) and can be regulated as required, and only is subjected to the influence of the geometrical shape of electric power and transmission line.By using suitable material, and provide good static sealing between transmitter (transducer) and transmission line, described system is highly suitable for rugged environment.Described system needs lower power, and the available TW two wire 4-20mA system that for example is used for process control industries operates.Such system utilizes the protocol communication technology, for example HART  and Fieldbus TMThe communication technology.
Although invention has been described with reference to embodiment, it will be appreciated by those skilled in the art that and under the situation that does not depart from the spirit and scope of the invention, can carry out variation form and details.

Claims (20)

1. one kind is used for measuring the device of hydraulic piston at the relative position of cylinder, comprising:
Along the bar that the piston motion direction is extended, described bar is fixedly connected in piston or the cylinder one of them, and described bar is constructed to deliver microwave pulse between the end of a connection piece and bar;
One slider, it is connected in described piston or the cylinder another slidably, and described sliding contact part is constructed to cause the partial reflection of microwave pulse;
Microwave transceiver circuit, it is connected to and is configured to produce and receive on the bar of microwave pulse; With
Counting circuit, its circuit structure can calculate piston position as the function from the reflected microwave pulse of sliding contact part and bar far-end.
2. device according to claim 1 is characterized in that, described bar comprises two conductors.
3. device according to claim 1 is characterized in that, described conductor is parallel substantially.
4. device according to claim 1 is characterized in that described slider is fixed on the piston.
5. device according to claim 1 is characterized in that described slider is fixed on the cylinder.
6. device according to claim 1 is characterized in that described bar is fixed on the cylinder.
7. device according to claim 1 is characterized in that described bar is fixed on the piston.
8. device according to claim 1 is characterized in that, described bar and described slider are arranged in cylinder.
9. device according to claim 1 is characterized in that, described bar and described slider are positioned at outside the cylinder.
10. one kind is used for measuring the device of hydraulic piston at the relative position of cylinder, comprising:
Along the bar that the piston motion direction is extended, described bar is fixedly connected in piston or the cylinder one of them, and the structure of described bar is for delivering microwave pulse between the end of a connection piece and bar;
One slider, it is connected in described piston or the cylinder another slidably, and described sliding contact part is constructed to cause the partial reflection of microwave pulse;
Microwave transceiver circuit, it is connected to and is configured to produce and receive on the bar of microwave pulse; With
Counting circuit, its circuit structure can calculate piston position as the function from the reflected microwave pulse of sliding contact part and boom end.
11. device according to claim 10 is characterized in that, described conductor comprises bar.
12. device according to claim 10 is characterized in that, described conductor comprises two bars.
13. device according to claim 12 is characterized in that, described bar is parallel substantially.
14. device according to claim 10 is characterized in that, described slider is fixed on the piston.
15. device according to claim 10 is characterized in that, described slider is fixed on the cylinder.
16. device according to claim 10 is characterized in that, described conductor is fixed on the cylinder.
17. device according to claim 10 is characterized in that, described conductor is fixed on the piston.
18. device according to claim 10 is characterized in that, described conductor and described slider are arranged in cylinder.
19. device according to claim 10 is characterized in that, described conductor and described slider are positioned at outside the cylinder.
20. device according to claim 10 is characterized in that, described piston is described conductor.
CN02809042.XA 2001-05-16 2002-05-15 Hydraulic piston position sensor Expired - Fee Related CN1250883C (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US29130601P 2001-05-16 2001-05-16
US60/291,306 2001-05-16
US09/991,817 2001-11-19
US09/991,817 US6588313B2 (en) 2001-05-16 2001-11-19 Hydraulic piston position sensor

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Publication Number Publication Date
CN1505738A true CN1505738A (en) 2004-06-16
CN1250883C CN1250883C (en) 2006-04-12

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US (1) US6588313B2 (en)
EP (1) EP1387964B1 (en)
JP (1) JP4176484B2 (en)
CN (1) CN1250883C (en)
DE (1) DE60205473T2 (en)
WO (1) WO2002093019A1 (en)

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CN103403363A (en) * 2011-02-28 2013-11-20 卡特彼勒公司 Hydraulic control system having cylinder flow correction
CN103403363B (en) * 2011-02-28 2016-10-12 卡特彼勒公司 There is the hydraulic control system of cylinder flow correction

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US6588313B2 (en) 2003-07-08
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EP1387964A1 (en) 2004-02-11
JP2004526112A (en) 2004-08-26

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